Refactor AppendToFile and WriteFileDescriptor

base/test/trace_to_file.cc

 // Copyright (c) 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/test/trace_to_file.h"
 
 #include "base/base_switches.h"
 #include "base/command_line.h"
 #include "base/debug/trace_event_impl.h"
 #include "base/files/file_util.h"
@@ skipping 49 matching lines @@
   const char str[] = "{\"traceEvents\": [";
   WriteFile(path_, str, static_cast<int>(strlen(str)));
 }
 
 void TraceToFile::AppendFileFooter() {
   const char str[] = "]}";
   AppendToFile(path_, str, static_cast<int>(strlen(str)));
 }
 
 void TraceToFile::TraceOutputCallback(const std::string& data) {
-  int ret = AppendToFile(path_, data.c_str(), static_cast<int>(data.size()));
-  DCHECK_NE(-1, ret);
+  bool ret = AppendToFile(path_, data.c_str(), static_cast<int>(data.size()));
+  DCHECK(ret);
 }
 
 static void OnTraceDataCollected(
     Closure quit_closure,
     debug::TraceResultBuffer* buffer,
     const scoped_refptr<RefCountedString>& json_events_str,
     bool has_more_events) {
   buffer->AddFragment(json_events_str->data());
   if (!has_more_events)
     quit_closure.Run();
@@ skipping 13 matching lines @@
   RunLoop run_loop;
   debug::TraceLog::GetInstance()->Flush(
       Bind(&OnTraceDataCollected, run_loop.QuitClosure(), Unretained(&buffer)));
   run_loop.Run();
 
   AppendFileFooter();
 }
 
 }  // namespace test
 }  // namespace base